Bath for plating bright copper



United States Patent BATH FOR PLATING BRIGHT COPPER Barnet D. Ostrow,North Bellmore, N. Y., assignor to Elechem Corp., Jersey City, N. J., acorporation of New Jersey No Drawing. Application June 4, 1956, SerialNo. 588,986

14 Claims. (Cl. 204-52) This invention relates to electroplating fromcyanide baths, more particularly to a bath composition which isparticularly adapted to produce bright coatings of soft, ductileelectroplates of copper.

Numerous attempts to obtain such bright coatings have been made. Forinstance, it has been proposde to use alkali metal selenite as anaddition agent to an electrolytic bath in relatively large amounts. Suchbaths had a number of disadvantages in that the selenites tended tobreak down with a resultant adverse effect on the bright plating range.the selenites, the anodes became blackened, forming insoluble compoundswhich were loosened from the anodes and tended to co-deposit with theplated metal, resulting in rough deposits which were commerciallyunusable. Also During the electrolysis because of breakdown of r 3 incommercial operation, due to the resulting very narrow 7 bright platingrange, non-uniform appearance of the deposits resulted, and the depositswere in many cases insufficiently bright so that buffing was necessary.

The present invention is intended and adapted to overcome thedifiiculties and disadvantages inherent in prior baths of the typedescribed, it being among the objects of the present invention toprovide a bath composition into which a relatively small amount ofaddition agents is introduced and which results in greatly increasedbrightness of the plated surface, with a wider, more uniform and brightplating range. t

It is also among the objects of the present invention to provide a bathcomposition which results in a plating which is brilliant, soft andductile and which may be readily buffed if desired to cause the coatingto flow, as for example, on steel.

It is further among the objects of the present invention to provide abath in which there is no breakdown even after long use.

The invention is based upon the discovery that the addition to a copperplating bath of very small amounts of selenium in the form of solublecompounds has a beneficial effect in the operation of the bath in orderto give bright deposits. The selenium compounds according to theinvention all have a valence of 2 and they may be either organic orinorganic compounds of selenium. The amount of such selenium compoundsadded is extremely small, ranging from .0001 to .01 gram per liter basedupon the selenium metal present in the compounds. The invention includesselenides of alkali metals and such other selenides which are soluble inthe bath. Various other inorganic selenium compounds having a valence of-2 which are soluble in the bath may be used. The organic seleniumcompounds may be the alkali metal selenocyanates, selenoureas,selenazoles and the like. Also included in the invention are compoundsof the formula RSeI-I wherein R is an organic radical having 1 to 6carbon atoms when the radical is alkyl and having 6 to 12 carbon atomswhen the radical is aryl.

Listed below are typical classes of compoundswhich are included in thepresent invention, illustrating the broad nature thereof:

Selencyanides (selenocyanates):

Na seleno-isocyanate K-selenocyanide NOz-phenyl selenocyanide Sedissolved in alkali metal cyanides.

Selenides:

Na and K monoand di-selenides Diamino-diphenyl-di-selenide Nazsee NazSeSelenoacids and salts (organic):

Selenoacetic Selenopropionic Selenoglycollic SelenobenzoicDiselenobenzoic Selenotartaric Selenocitric Seleno oxalic Selenoacidsand salts (inorganic):

Na selenophosphite K selenostannate Na selenopersulphate Kmonoselenothiosulphite K seleno diphosphite Selenoamines and amides:

Ethylamineethyl-diselenocarbama1e Selenourea K-selenoamide Diquinolineselenide Seleno xanthates:

K-selenoxanthate Selenols (alcohols):

Ethyl selenol Ethylene selenoglycol Selenophene:

Selenophene Z-sulphonic acid Selenophene 2-selenic acid Selenoazoles:

2-selenoth-iazoline 2-seleno selanazoline Z-methylbenzo selenazoleExample 1 There is provided a cop-per cyanide plating bath containingsodium diselen-ide and having the following compositions:

CuCN

Total KCN Free KCN Dipotassiurn tartrate 45.0 KOH 1-5.0 NazSez .0003(Se) Example 2 The bath containing potassium selenocy-anate has thefollowing composition:

CuCN 60.0 Total KCN 84.0

KOH 30.0 Free KCN -15 KCNSe .001 (Se) Example 3 In the followingcomposition the addition of the selenium is in the form of selenophenol.

CuCN

Total NaON 90.0 Rochelle salts 45.0

KOH 15.0 Free NaCN 7.5 Selenophenol .002 (Se) Example 4 The followingcomposition contains potassium selenide and an amino acid compound.

Example 6 The selenium present in the bath may be an organics-elenocyana'te, the bath having the following composition:

Copper cyanide 45 Total KCN 72 Free KCN 9-12 KOH Rochelle salts 45o-Nitro-phenyl selenocyanate .008 (Se) Example 7 The fol-lowing bathcontains the selenium in the form of quaternary selenazol.

Copper cyanide 45 Free NaCN 10 Rochelle salts 45 KOH 15Z-methylbenzoselenazole ethiodide .01 (Se) Example 8 Various inorganicselenium compounds are suitable for the purpose as in the followingcomposition, which contains the selenium in the form of a thiosulphiteof the formula KzSeSOs.

Copper cyanide 75 KCN 105 K tartra te 40 Free KCN 8 KOH 15 KMonoselenothiosulphite .005 se Example 9 The following compositionillustrates the use of a selenide in organic form:

Copper cyanide 60 Total KCN 84 KOH 30 Free KCN 120,0'-Diamino-diphenyl-diselenide .007 (Se) Example 10 The selenium maybe in the form of a phosphite, for instance, having the formula2K2Se.P2Se3, as illustrated in the following composition:

Copper cyanide 45 Total KON 71 Free KCN 8 Rochelle salts 20 KzCOs 30 Kselenodiphosphite .002 (Se) Example 1] Baths containing relativelylarger amounts of the selenium compounds may be used as, for instance,the following bath:

CuCN 56.0 Total KCN 82.0 Free KCN 28.0 Selenobenzoic acid .04 (Se)Example 12 The following bath contains a substantial amount of aninorganic complex selenium salt.

CuCN 60.0

Total KCN 94.0 K carbonate 30.00 Free KCN 10.0 Rochelle salts 20.0 Naselenostannate .02 (Se) Example 13 A typical bath containing aSelene-alcohol is the following:

CuCN 45.0 Total KCN 72.00 Free KCN 9-12 KOH 15.0 Rochelle salts 45.0Ethyl selenol .05 (Se) Example 14 The following is a similar bath inwhich the selenium is in the form of a xanthate:

CuCN 75.0 Total KCN 105.0 Free KCN 8.0 KOH 15.0 K tartrate 40.0 Naselenoxanthate .04 (Se) Example 15 Selenium in the form of thiazolecompounds are also suitable as illustrated by the following formula:

CnCN 45 .0 Free NaCH 10.0 Rochelle salts 45 .0 KOH l5 .0-selenothiazoline 01 (Se) Example 16 Sulphonic acids and their solublesalts containing selenium are satisfactory as shown by the followingcomposition:

CuCN 55.0 Total KCN 80.0 Free KCN 12.0 KOH 28.0 Selenophene-2-sulphonicacid Na salt .007 (Se) In the preferred form of the invention the amountof selenium is generally not over .01 gram per liter and sufficient togive a brightening effect. But larger amounts may be used as shown inExamples 1114; however such larger amounts do not usually contributesufficiently to the brightening effects to warrant the added costinvolved, so that ordinarily the smaller amounts have been found to bemost satisfactory.

The effectiveness of the above baths continues over long periods of timeas to stability and bright ranges. in contrast to baths containing theselenium having valences of +4 or +6, such as selenites or selenates,which have a narrow bright range and rapidly lose their effectiveness inthe bath under normal operating conditions. They are unstable compoundswhich darken the anode, cause the cathode to become non-uniformly dull,have a narrow bright range and tend to give rough deposits, whereasthose selenium compounds having a valence of 2 do not show such defects.

Although the invention has been described setting forth several specificexamples of the operation thereof, the invention is not to be limitedthereto as many changes may be made in the details thereof. Forinstance, the composition of the baths may be considerably altered andother substances may be added thereto, such as alkyl polyamines,including ethylene diamine, diethylene triamine, triethylene tetramine,and others up to alkyl groups having 5 carbon atoms, the number of aminogroups being from 2 to 5, in amounts of about .25 to 50 grams per liter,although preferably smaller amounts up to 10.0 are used.

There may be added to the bath a surface active agent which is thecondensation product of ethylene oxide and an organic hydroxy compound.Such an agent has the general formula RO(C2H4O)H wherein R is ahydrocarbon radical having 5 to carbon atoms and x is a numeral from 10to 80. The conditions of operation of the plating bath may be variedwithin usual practice. Larger amounts of the additive may be used, evenabove the maxima stated herein. However, such excess does not usuallygive beneficial effects.

The present application is a contimiation-in-part of my copendingapplication Ser. No. 479,871 filed January 4, 1955, which is acontinuation-impart of my application Ser. No. 349,935, filed April 20,1953, Patent No. 2,732,336, said patent being a continuation-impart'ofapplication Ser. No. 126,679, now Patent No. 2,694,677,

dated November 16, 1954, entitled Bright Copper Plating Bath, which inturn is a continuation-in-part of abandoned application Ser. No. 6,354,filed February 4, 1949, and entitled Electro-Deposition of a BrightCopper.

I claim:

1. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble selenium compound in which the seleniumhas a valence of 2 in amount sufficient to exert a brightening effect onthe copper deposit.

2. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble selenium compound in which the seleniumhas a valence of 2 in amount sufficient to exert a brightening effect onthe copper deposit, the amount being from .0001 to .05 gram per liter ofelemental selenium.

3. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble selenium compound in which the seleniumhas a valence of 2. said selenium compound being present in an amountfrom .0001 to .01 gram per liter of elemental selenium.

4. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a. soluble inorganic selenium compound in whichthe selenium has a valence of 2, said selenium compound being present inan amount from .0001 to .01 gram per liter of elemental selenium.

5. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble organic selenium compound in which theselenium has a valence of -2, said selenium compound being present in anamount from .0001 to .01 gram per liter of elemental selenium.

6. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble inorganic selenium compound in whichthe selenium has a valence of 2, said selenium compound being present inan amount from .0001 to .01 gram per liter of elemental selenium, saidcompound being taken from the class consisting of inorganic selenides,selenocyanates, selenophosphites and selenothiosulphites.

7. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble organic selenium compound in which theselenium has a valence of 2, said selenium compound being present in anamount from .0001 to .01 gram per liter of elemental selenium, saidcompound being taken from the class consisting of organic selenonreas,selenocyanates, selenoazoles, selenides, and compounds of the formulaRSeH wherein R is an organic radical having 1 to 6 carbon atoms whensaid radical is alkyl and having 6 to 12 carbon atoms when said radicalis aryl.

8. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper containing from .0001 to .01 gram per liter ofelemental selenium in the form of selenourea.

9. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper containing from .0001 to .01 gram per liter ofelemental selenium in the form of alkali metal selenocyanate.

10. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper containing from .0001 to .01 gram per liter ofelemental selenuim in the form of alkali metal selenide.

11. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper containing from .0001 to .01 gram per liter ofelemental selenuim in the form of an organic selenide.

12. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper containing from .0001 to .01 gram per liter ofelemental selenium in the form of a compound selected from the groupconsisting of a selenol and the soluble salt thereof.

13. An electrolytic bath comprising an aqueous alkaline solution of acyanide of copper, and a soluble selenium compound in which the seleniumhas a valence of 2, said selenium compound being present in an amountfrom .0001 to .05 gram per liter of elemental selenium, and an alkylpolyamine.

14. An electrolytic bath comprising an aqueous all aline solution of acyanide of copper, and a soluble selenium compound in which the seleniumhas a valence of 2, said selenium compound being present in an amountfrom .0001 to .05 gram per liter of elemental selenium, and apolyethylene glycol ether.

References Cited in the file of this patent UNITED STATES PATENTS2,384,300 Harford Sept. 4, 1945 2,582,233 Chester et a1 Ian. 15, 1952,677 Ostrow Nov. 16, 1954

1. AN ELECTROLYTIC BATH COMPRISING AN AQUEOUS ALKALINE SOLUTION OF ACYANIDE OF COPPER, AND A SOLUBLE SELENIUM COMPOUND IN WHICH THE SELENIUMHAS A VALENCE OF -2 IN AMOUNT SUFFICIENT TO EXERT A BRIGHTENING EFFECTON THE COPPER DEPOSIT.